Global gyrokinetic simulations of electrostatic microturbulent transport in LHD stellarator with boron impurity

Abstract

Global gyrokinetic simulations of electrostatic microturbulent transport for discharge # 166256 of the Large Helical Device stellarator in the presence of boron impurity show the co-existence of the ion temperature gradient (ITG) turbulence and trapped electron mode (TEM) turbulence before and during boron powder injection. ITG turbulence dominates in the core, whereas TEM dominates near the edge, consistent with the experimental observations. Linear TEM frequency increases from ∼ 80 kHz to ∼ 100 kHz during boron injection, and ITG frequency decreases from ∼ 20 kHz to ∼ 13 kHz, consistent with the experiments. The poloidal wave number spectrum is broad for both ITG (0–0.5 mm−1) and TEM (0–0.25 mm−1). The nonlinear simulations with boron impurity show a reduction in the heat conductivity compared to the case without boron. The comparison of the nonlinear transport before and during boron injection shows that the ion heat transport is substantially reduced in the region where the TEM is dominant. However, the average electron heat transport throughout the radial domain and the average ion heat transport in the region where the ITG is dominant are similar. The simulations with boron show the effective heat conductivity values qualitatively agree with the estimate obtained from the experiment.

Gyrokinetic simulations of electrostatic microturbulence in ADITYA-U tokamak with argon impurity

“…to simulate the micro-instabilities in LHD [32,43], W7-X [44] stellarators, and tokamak [37]. In this model, the electron distribution function is written as a sum of adiabatic and non-adiabatic parts, f e = f 0 e eϕ/Te + δg e .…”

“…To this end, high-fidelity gyrokinetic simulations of magnetic fusion devices have proven to be an invaluable tool in studying transport induced by low frequency microturbulence [31]. For example, recently, the gyrokinetic toroidal code (GTC) has been used to validate the boron powder injection experiment in LHD [32] where the improved plasma confinement is observed [8]. Here, GTC is a Lagrangian approach-based particle-in-cell (PIC) code developed to study the transport due to microturbulence [33], Alfvén eigenmodes [34], radio frequency waves [35], and the energetic particles [36].…”